Stop motion for knitting machines



Nov. 5, 1946. A. CRAWFORD 2,410,718

S TOP MOTION FOR KNITTING. MACHINES Filed Jan. so, 1946 2 Sheets-Sheet;1.

Nov. 5, 1946. A. CRAWFORD 2,410,713

STOP MOTION FOR KNITTING MACHINES Filed Jan. 50, 1946 2 Sheets-Sheet 2Patented Nov. 5, 1946 2,410,718 STOP MOTION FOR KNITTING MACHINES AlfredCrawford,

New Brunswick, N. J., assignor to Crawford Manufacturing Company, NewBrunswick, N. J a corporation of New Jersey Application January 30,1946, Serial No. 644,288

4 Claims.

This invention relates to improvements in stop motions for knittingmachines and more particularly to improvements specific .to the type ofstop motion produced and marketed by the Crawford Manufacturing Companyof New Brunswick, New Jersey, whose commercial product is disclosed ingeneral in a prior patent to Alfred Crawford, No. 1,992,860, datedFebruary 26, 1935, while certain details of the device are disclosed inaprior patent to Michael Antonevich, No. 2,257,030, dated September 23,1941, of which, inv each instance, the Crawford Manufacturing Companyisthe assignee exclusively.

In each of the structures disclosed, respectively, in the aforesaidpatents, the very uppermost partof the stop motion is in the form of aspider including alarge central hub portion from which a number of armsradiate. In each instance, the outer end of the arm supports a threadcontrolled device which willoperate to effect stopping of the knittingmachine should the knitting thread or yarn become too tight, too loose,or break.

The thread controlled fingers of the entire series carried respectivelyby the radiating spider arms, operate a common control mechanism housedwithin the hub of the spider. Thus, in initial installation, it requiresthat a complete assembly of all the thread controlled mechanisms,including a switch operating element individual to each, and a switchactuating ring common to all, mustbe made before the device as a wholecan be adjusted for operation with the knitting to which the stop motionis applied.

In the prior patent to Crawford, aforesaid, it will be noted that thereis a second series of thread controlled switches housed in a hollowannular casing located above, but in relatively close proximity to theknitting head of the machine to which the stop motion is applied. Theselower switches are subject to becoming fouled by lint, etc., enteringthrough various openings in the annular casing, etc., through whichcertain elements of the device extend.

The present invention is directed to the provision of an improved typeof switch structure adapted to replace both the top switches and thelower switches of the stopmotion which asa whole is disclosed in theaforesaid Crawford patent. Primarily, the new switches are adapted to becompletely enclosed in dust-proof casings to prevent entrance of lintand the fouling of the switch mechanism. Furthermore, the constructionis such that the switches maybe preassembled and adjusted individuallyand held in stock for future assembling or as replacements in the stopmotions as a whole. The principles upon which .both the top and bottomswitches of the present invention are constructed are sub- Fig. 4 is aside elevation, partly in section, of

the upper switch unit, with thecover plate ;re-, moved;

Fig. 5 is a transverse section taken on the line 5-4, Fig. 4.; and

Fig. 6 is a transverse section taken on the.

line i: -6, Fig. 4.

The new bottom switch, as shown in Figs. 1,

2, and 3 of theattached drawings, includes a dust-proof casing I inwhich is mounted a transverse shaft 2 having a sweep arm or feeler wire4 secured to one end thereof outside the casing I, The free end of thesweep wire 4 is provided with a thread. eye 5 operating between fixedthread eyes 6, 6, through all three of which extends the knitting threada: on its way to the knitting head of the machine.

Within the casing l the shaft 2 is provided with a crank which bearsagainst a cam surface 8 on a long arm 9 of a bell crank lever which ispivoted at Ill within the casing l. The short arm ll of the bell cranklever has attached thereto one end of the tension spring l2, theopposite end of which is soldered or otherwise secured to a block [3which is slidably mounted in the casing I, and is adjustable by a screwM from outside the casing I. Obviously by adjust-v ing the screw [4 anydesired degree of tension may be placed on the sweep arm 4, constantlytendin to swing it in the directionv of the arrow in Fig. 2, wherebymore or less tension is applied to the thread r between the fixed guidesv6, 6. Due to the relation between the long and short arms of the bellcrank lever, very little axial extension of the spring 12 is required,and this provides uniform tension on the outer end of the sweep arm atall times through a rather long movement of the outer end of the sweeparm.

Should the yarn a: break, or become excessively slack at 01' near theknitting head, the free end 5 ofthe sweep arm 4 will be released and thespring l2 acting through the bell-crank ll- 9 will cause the cam face 8of the long arm 9 to force the crank I downwardly, fromits full line,

position shown in Fig. 2, 'to'its broken line position shown in saidfigure, to permit the tip 9a of the arm 9 to make electrical contactwith a resilient contact I5.

The weight of the sweep arm 4 is substantially counterbalanced by anoff-center weight I2a applied to the protruding end of the operatinshaft 2, in order to make the action of the tension spring I2 moresensitive.

The contact I5 is secured by a shouldered rivet I6 to an insulatingblock II, secured in the box I by a screw I8. The larger diameteredportion I9 of the rivet I6 passes through an oversized hole in the endwall of the box I and is connected by a screw 22 to an angle strap 2|,which in turn is electrically connected to a buss bar 23 forming part ofone side of the circuit for the electric knock-off mechanism (not shown)of the stop motion, the box I, etc, being included in the second side ofthe circuit.

The boxes I are each provided with a slotted lug 24 adapted to beadjustably bolted to a supporting ring 25, similar to a correspondingring of the Crawford patent aforesaid.

Obviously the switch mechanisms may be completely assembled in the boxesI and adjusted ready to be applied subsequently to the supporting ring25 on machines having any prevailing number of yarn feeds, with oneswitch assembly for each feed. All the adjustment required, after theboxes I are in place, would be to bend the sweep wires 4 to bring theeye 5 in proper relation to the fixed eyes 6, 6.

The eyes 6, 6 are supported by arms 26, like the corresponding arms ofthe Crawford patent aforesaid, and these arms may be attached to covers21 of the boxes I durin remote assembly of the switch mechanismstherein, or the arms may be connected directly to the boxes I or to thesupporting ring 25, as desired.

In the top switch shown in Figs. 4, 5, and 6 of the drawings, all of themechanism is confined in the boxes Ia and these boxes are separatelyconnected to the spider arms I I6 of the aforesaid Crawford patent orthe corresponding arms of the aforesaid Antonevich patent, thuseliminating the two coaxial shafts disclosed in said patents and whichextend longitudinally of each spider arm; and also eliminating all ofthe switch mechanisms confined in the hubs from which the spider armsproject.

These upper switch mechanisms are substantially the same as the lowerswitch mechanisms previously described as being confined in the boxes I,and the same reference characters are here now employed. However,instead of the operating shaft, as the shaft 2 in the lower switchmechanism being parallel to the pivot l0 for the bell crank B-I I, theoperating shaft 2a of the upper switch mechanism projects into thecasing Ia through one end wall thereof, at right angles to the axis ofthe pivot Illa of the bell crank 9a II a, therefore the long arm 9a isprovided with a right angle extension 91) against which the crank Ia ofthe shaft 2a bears. The sweep arm 4a is normally urged in the directionof the arrow in Fig. 6 by a resiliently mounted arm 28, whichcorresponds to the same kind of arm as shown in the Antonevich patentaforesaid.

If the yarn a: breaks or becomes excessively slack, the resilientlymounted arm 28 moves the sweep arm 4a upwardly turning the shaft 2a andcrank 1a accordingly, permittin the right angular extension 9b of thelong arm 9a of the bell crank 9a-I Ia under the influence of the springI2 and weight I2a, to engage the resilient contact I5a, closing thecircuit between the buss bar 23a and the casing Ia to actuate theelectric knock-off of the stop motion.

If the yarn should become excessively taut, the sweep arm do will bemoved downwardly turning the shaft 2a and its crank 1a accordingly andforcing the right angular extension 9b of the bell crank 9a-IIa intocontact with a second resilient contact I5b which also closes thecircuit for actuating the electric knock-off of the stop motion.

It will be understood that the feeler 4 or 4a, as the case may be, isextremely sensitive to fluctuations in the tension of the running yarn2:. It also detects the presence or absence of a running yarn and in anyinstance of unnormal eventuality effects the proper reactions in theapparatus as a whole to stop the machine.

The bell-crank lever, which in effect constitutes a rotary switchelement having one portion adapted to engage the electric terminalelement I5 is extremely sensitive, and this sensitivity is maintaineduniform by reason of the axis of the tension spring I2 beingsubstantially tangent to the are described by the point of attachment ofthe one end of the spring I2 with the short arm I I of the bell-cranklever, due to the fact that such point travels but a very short distanceand not sufficient to produce any substantial elongation of the springI2.

I claim:

1. A switch structure for electric stop motions for knitting machinesand the like, comprising a closed casing, an operating shaft pivoted inand having one portion projecting outside said casing, a bell-cranklever pivoted and confined within said casing, a tension springoperatively eonnected to one arm of said belLcrank lever and confinedwithin said casing, an electric terminal element within said casing andengageable by a second arm of said bell-crank lever, a crank on theportion of the operatin shaft disposed within said casing and engageablewith one of said arms, and a thread engaging sweep arm secured to thatportion of the operating shaft disposed outside said casing.

2. A structure according to claim 1, characterized by the bell-crankhaving a long arm and a short arm, with the tension spring connected tosaid short arm and the crank of the operating shaft engageable with saidlong arm.

3. A structure accordin to claim 1 characterized by the tension springbeing partially opposed by an eccentric Weight on the protruding portionof the operating shaft and partially counterbalancing the weight of thesweep arm, to make the tension spring more sensitive to fluctuations inthe tension of the knitting yarn.

4. In a switch structure, the combination of a substantially fixedelectric terminal element, a relatively rotatable switch element adaptedto have one portion thereof engageable with said terminal element andcomprising a bell-crank lever including a short arm and a relativelylong arm, a tension spring operatively connected to said short arm withthe axis of said spring substantially tangent to the arc of travel ofthe point of attachment of one end of the spring to said short arm tomaintain the applied tension of said spring uniformly sensitive, and afeeler element engageable with and adapted to actuate said switchelement into contact with said terminal element by overcoming saidtension of said spring.

ALFRED CRAWFORD.

